28 lines
609 B
Plaintext
28 lines
609 B
Plaintext
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%
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%% simple constraint solver for inequalities between variables
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%% thom fruehwirth ECRC 950519, LMU 980207, 980311
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%%
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%% ported to hProlog by Tom Schrijvers
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:- module(leq,[leq/0]).
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:- use_module(library(chr)).
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:- chr_constraint leq/2.
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reflexivity @ leq(X,X) <=> true.
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antisymmetry @ leq(X,Y), leq(Y,X) <=> X = Y.
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idempotence @ leq(X,Y) \ leq(X,Y) <=> true.
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transitivity @ leq(X,Y), leq(Y,Z) ==> leq(X,Z).
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leq :-
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circle(X, Y, Z),
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\+ attvar(X),
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X == Y,
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Y == Z.
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circle(X, Y, Z) :-
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leq(X, Y),
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leq(Y, Z),
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leq(Z, X).
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